Facilitating secure online transactions

ABSTRACT

A method and system for mutually authenticating an identity and a server is provided in accordance with an aspect of the present invention. The method commences with transmitting a token from the server. Thereafter, the method continues with establishing a secure data transfer link. A server certificate is transmitted during the establishment of the secure data transfer link. The method continues with transmitting a response packet to the server, which is validated thereby upon receipt. The system includes an authentication module that initiates the secure data transfer link and transmits the response packet, and a server authentication module that transmits the token and validates the response packet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/702,371 filed on Feb. 5, 2007 which claims priority to U.S.Provisional Application No. 60/827,118 filed Sep. 27, 2006. The entiredisclosure of these priority applications are hereby incorporated byreference herein in their entirety.

BACKGROUND

1. Technical Field

The present invention generally relates to methods and systems forauthentication in secure data communications.

More particularly, the present invention relates to methods and systemsfor bi-directionally authenticating the client and the server using aplurality of factors including a public key infrastructure (PKI)certificate.

2. Related Art

Banking, financial services, government, education, and all varieties ofcompanies rely upon advanced computer systems and data communicationnetworks such as the Internet. While such advancements have greatlyincreased the speed and convenience with which business is conducted,numerous vulnerabilities compromise the security of the highly sensitiveand confidential data being exchanged. At the most basic level,electronic transactions typically involve a server computer system and aclient computer system communicating over a network. Additional clientor server computer systems may also be connected to the network, suchthat multiple clients may access a given server, or multiple servers maybe accessed by a given client. In this open network environment, theprimary concern of data security is three-fold. First, the server mustbe assured that the client is what it asserts it is. Second, the clientmust be assured that the server is what it asserts it is. Third, anyinformation being exchanged between a legitimate server and a legitimateclient must not be intercepted or changed by any other computer systemson the network.

In the electronic banking setting, for example, the bank mustauthenticate the identity of the user accessing the banking server, sothat transactions relating only to a particular customer are permitted,and that the user accessing the banking server is verified as thecustomer or someone given authority by the customer. The client must beensured that the banking server is, indeed, the server operated by thebank, and not a similar one operated by a malicious entity. This isknown as a phishing attack, where a fake server is made to resemble thelegitimate server, and tricks the user into providing confidentialinformation such as bank account numbers, social security numbers,passwords, and the like. Much harm may be inflicted on the customer by acriminal possessing such information, including erroneous accumulationof debt, arrest records, criminal convictions, destruction ofcreditworthiness, damage to reputation, and so forth. These are alsoknown as identity theft crimes. As confidential information is beingtransmitted over an open network, such information must be encrypted orotherwise rendered incomprehensible to any other system besides theclient and the server. The open nature of the network renders computersystems susceptible to replay attacks, where a valid data transmissionis intercepted and repeated later for fraudulent or malicious purposes.For example, passwords or other authentication information may beintercepted, and used later to gain access to sensitive information.Further, the information being transmitted on the network must not bemodifiable, such as in the case of man-in-the-middle attacks. Thisinvolves an attacker reading, inserting and modifying data between alegitimate client and server with neither recognizing the compromisednature of the link.

A variety of techniques is used to authenticate, or verify the identityof the client. Authentication may utilize one or more factors, whichinclude something a user knows, something a user has, and something auser is. Most often, only a single factor is utilized because of theadded cost and complexity of additional authentication factors. In suchsingle-factor authentication systems, the most common is the use of apassword or a personal identification number (PIN) to limit access.Another example is an ATM card with a corresponding PIN. The servermaintains a list of usernames and corresponding passwords/PINs, and whenthe entered username and password/PIN combination is determined to becorrect after a comparison to the list, access to the system ispermitted. The secret nature of passwords and PINs, at least in theory,prevents unauthorized users from accessing the computer system. Thistechnique is ineffective because the authorized users oftentimesmistakenly and unwittingly reveal their passwords or PINs to anunauthorized user. Furthermore, brute-force techniques involving theentry of every combination of letters, numbers, and symbols, as well asdictionary-based techniques, may further compromise the effectiveness ofsuch authentication systems. Because passwords must be memorized, usersoften choose words that are easier to remember, making it moresusceptible to defeat by means of dictionary attacks. On the other hand,the more complex the passwords are required to be, the more likely thatthe password will be written on something easily accessible, for boththe legitimate and malicious user, in the vicinity of the computer. Asasserted by the Federal Financial Institutions Examination Council(FFIEC), single factor authentication is a substantial weakness,particularly in financial or banking-related on-line services.

In addition to passwords, an additional factor may be utilized thatinvolves something a user has. These include simple devices that areconnected to the client computer through an external peripheral port, aswell as sophisticated tokens that generate unique codes or one-timepasswords (OTP) that are that are entered in conjunction with a usernameand a password as described above. Currently available token-basedauthentication systems include the RSA SecureID, which utilizes atime-synchronized OTP, and the Verisign Unified Authentication, whichutilizes a mathematical algorithm-based OTP. While greatly increasingsecurity, token devices are expensive to license, expensive to maintain,and cumbersome for the user to carry. As with any diminutive device,tokens are easy to lose. When lost, it may take days or weeks for areplacement, resulting in additional cost and lost productivity.

A third authentication factor utilizes unique biometric attributes of aperson, such as fingerprints, retinal and facial patterns, voicecharacteristics, and handwriting patterns. Biometric authentication,however, requires the deployment of specialized hardware for acquiringsuch data including fingerprint and retina scanners, microphones, andthe like. Furthermore, specialized databases and software are requiredfor comparing the acquired data to existing user data, otherwisereferred to as enrollment data. Thus, the cost of such deployment isprohibitive, and is for the most part limited to large organizations.Additionally, biometric readings may be inconsistent from oneacquisition to the next, thereby resulting in false negatives. Thoughfingerprint identification is being increasingly used in portablecomputers to secure access to applications and data therein, the use ofsuch devices to authenticate with other computer systems is uncommonbecause of the need to maintain an enrollment database.

To authenticate the server computer system, and to ensure that datatransmissions are not intercepted, the Transport Layer Security (TLS)protocol is frequently utilized. TLS is a cryptographic protocol thatprovides data exchanges safe from eavesdropping, tampering, and forgery,and is often used for securing web browsing, e-mail, file transfers, andother such electronic transactions. More particularly, TLS operates onthe protocol layers below application-layer protocols such as theHyperText Transfer Protocol (HTTP), File Transfer Protocol (FTP), SimpleMail Transfer Protocol (SMTP), but above the transport level protocolssuch as the Transmission Control Protocol (TCP) or the User DatagramProtocol (UDP). Various components of a public key infrastructure (PKI)conforming to the International TelecommunicationsUnion-Telecommunications Standardization Sector (ITU-T) PKI standardX.509 are utilized in the TLS protocol.

Generally, public key encryption involves a unique public/private keypair held by both the recipient and the sender. The private key of thesender is retained solely by the sender, and the private key of therecipient is retained solely by the recipient. The public key of thesender is distributed and is held by the recipient, and the public keyof the recipient is also distributed and held by the sender. Whentransmitting a message, the sender's private key and the recipient'spublic key is used to encrypt the message. The message is decrypted bythe recipient using the recipient's private key and the sender's publickey. The recipient need not have a unique public/private key pair,however, and instead may utilize a one-time cipher.

TLS is commonly implemented only on a server-side basis, however, andonly the server is authenticated. For example, when establishing asecure HyperText Transfer Protocol (HTTP) connection from a clientbrowser to a web server, the client browser retrieves a digitalcertificate associated with the web server. The certificate, whichcontains the public key, is used by the browser to authenticate theidentity of the web server, and to encrypt a session key transmittedback to the web server for use in encrypting subsequent data. In orderto ensure the legitimacy of the server certificate, it is signed by aCertification Authority (CA).

Though the implementation of client-side TLS establishes a bilateraltrust between the server and the client and prevents identity theft andphishing attacks, there are a number of significant deficiencies. Moreparticularly, it is necessary for the client to obtain or purchase acertificate properly signed by the CA. Thus, complications associatedwith certificate ownership are placed on the user. Additionally,implementing client authentication on the server is a cumbersomeprocess, in that additional servers and maintenance is necessary. Inaddition to the other core functionality provided by the server, it mustbe configured to issue user certificates.

Accordingly, there is a need in the art for a method and system forauthenticating the client and the server without the use of hardwaredevices such as tokens or the deployment of client-side TLS. There isalso a need for such authentication to be over multiple factors.Furthermore, there is a need for an improved method and system forinitiating an encrypted data communications session using authenticationcredentials. There is also a need in the art for an authenticationsystem that is easy to configure and readily integrates with existingservers and clients.

BRIEF SUMMARY

According to an aspect of the present invention, there is provided amethod for mutually authenticating a client and a server. The method maybegin with transmitting a token from the server to the client.Additionally, the method may include establishing a secure data transferlink between the server and the client. A server certificate may betransmitted to the client during the establishment of the secure datatransfer link. The method may continue with transmitting a responsepacket to the server, which may include a full requested UniformResource Locator (URL) identifier, a client certificate, the servercertificate, and the token. Additionally, the response packet mayinclude an authenticity identifier signed with a private key. The methodmay also include validating contents of the response packet.

Since the authentication is conducted separately from the secure datatransfer link, there is no need to convert websites for client-sideauthentication. Additionally, no user action is required to store orretrieve the client certificate, greatly simplifying certificatemanagement on the client without compromising security.

According to another aspect of the present invention, the method maycontinue with validating the response packet may involve validating thefull requested URL identifier in the response packet against a URLassociated with the server. Further, validating the response packet mayalso involve validating the token in the response packet against a tokenstored on the server. The token in the response packet and the tokenstored on the server may contain a unique code. The method of validatingthe response packet may also involve validating a first copy of theserver certificate stored on the server against a second copy of theserver certificate in the response packet. Additional validation mayinclude validating the client certificate against a client signature onthe response packet. The client signature may be associated with theprivate client key. These validations ensure that the communicationbetween the client and the server is secure, and not susceptible toman-in-the-middle and/or replay attacks, where tampering with thecontents of the response packet may occur. Where any of the foregoingvalidations fails, the connection is deemed to have been compromised,and no further transmissions will occur.

The client certificate may be issued from a certificate serverassociated with an authorized certification authority, and the clientmay be linked to an organization associated with the server. Prior toissuing the client certificate, the method for mutually authenticating aclient and a server may include validating the client with achallenge-response sequence. A response to the challenge-responsesequence may be transmitted to a predetermined telephone deviceassociated with a user, or may be transmitted to a predetermined e-mailaddress associated with the user. As such, there is no need for anorganization to issue, manage, and track revocations of certificates.Along these lines, there is no need for an organization to install andconfigure the server for client-side authentication.

According to another aspect of the present invention, a system forbi-directionally authenticating a client and a server is provided. Thesystem may include a server authentication module associated with theserver. The server authentication module may include a memory forstoring a server certificate and a token. Furthermore, the serverauthentication module may be operative to transmit the token and theserver certificate to the client. In yet another aspect of the presentinvention there is provided a client authentication module associatedwith the client. The client authentication module may include a memoryfor storing a client certificate, the token, a full requested URLidentifier, and the server certificate, and may be operative to transmitan authentication packet including the server certificate, the token,and the full requested URL identifier. The authentication packet may besigned with the client certificate.

The present invention will be best understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is a block diagram illustrating an environment in which oneaspect of the present invention may be implemented, including variousinterconnected servers and clients;

FIG. 2 is a flowchart illustrating a method for bi-directionallyauthenticating a client and a server in accordance with an aspect of thepresent invention;

FIG. 3 is a sequence diagram illustrating the exchange of data forauthenticating the client and the server;

FIG. 4 is a sequence diagram illustrating the establishment of aTransport Layer Security (TLS) connection between the client and theserver;

FIG. 5 is one embodiment of a digital certificate in accordance with anaspect of the present invention including various subparts thereof;

FIG. 6 is one embodiment of a response packet including a usercertificate, a full requested URL, a token, and a server certificate;

FIGS. 7 a-c is a flowchart illustrating the verification of the responsepacket;

FIG. 8 is a first exemplary configuration of the mutually authenticatingclient and server where the certificate and telephony servers arecontrolled by a third party provider;

FIG. 9 is a second exemplary configuration of the mutuallyauthenticating client and server in which the certificate and telephonyservers are controlled by an organization controlling the server; and

FIG. 10 is a third configuration of the mutually authenticating clientand server where secure access to web services is provided.

Common reference numerals are used throughout the drawings and thedetailed description to indicate the same elements.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be constructed or utilized. Thedescription sets forth the functions and the sequence of steps fordeveloping and operating the invention in connection with theillustrated embodiment. It is to be understood, however, that the sameor equivalent functions and sequences may be accomplished by differentembodiments that are also intended to be encompassed within the spiritand scope of the invention. It is further understood that the use ofrelational terms such as first and second, and the like are used solelyto distinguish one from another entity without necessarily requiring orimplying any actual such relationship or order between such entities.

With reference to FIG. 1, an exemplary computer network 10 includesvarious data processing apparatuses or computers 12, 14. Moreparticularly, the computers 12 may be personal computers or workstationsthat function as clients, and include a system unit 16 that houses acentral processing unit, storage devices, and the like. The computers 12may also include a display unit 18, and input devices 20 such as akeyboard 20 a and a mouse 20 b. It is understood that the system unit 16receives various inputs from the input devices 20 that alter the controland flow of preprogrammed instructions being executed by the centralprocessing unit, and the results of such execution are shown on thedisplay unit 18. The computers 14 may be servers that provide data orservices to the client computers 12. In this regard, the term “client”is understood to refer to the role of the computers 12 as a requestor ofdata or services, while the term “server” is understood to refer to therole of the servers 14 to provide such data or services. Additionally,it is possible that the computers 12 may request data or services in onetransaction and provide data or services in a transaction, thus changingits role from client to server or vice versa.

The computers 12, 14 are connected to a wide area network such as theInternet 22 via network connections 24. Requests from the clientcomputers 12 and requested data from the server computers 14 aredelivered through the network connections 24. According to an embodimentof the present invention, the server computers 14 are web servers, andthe client computers 12 include web browsing applications such asMicrosoft Internet Explorer that visually renders documents provided bythe server computers 14 on the display unit 18. It will be appreciatedthat the network topology shown in FIG. 1 is presented by way of exampleonly and not of limitation, and any other type of local or wide areanetwork may be readily substituted without departing from the scope ofthe present invention. It is understood that any well known datatransmission protocol may be utilized for the network connections 24 andthe internet 22.

As a further example, a first server computer 14 a may be an electronicbanking web server that provides account information and funds transferfunctionality. Additional uses are also contemplated, where the firstserver computer 14 a hosts a mail server, an online shopping site, or aMicrosoft .NET application. A user on the first client computer 12 a maylog on to first server computer 14 a to retrieve the account balance andtransfer funds to a separate account using a web browser. In thisexemplary context, one of the considerations of information securityincludes ensuring that the user on the first client computer 12 a is whohe asserts to be. For example, a malicious user on a second clientcomputer 12 b may have all of the credentials of the user on the firstclient computer 12 a to log on to the first server computer 14 a withoutrecognizing that such access is fraudulent. Another consideration isensuring that the first server computer 14 a is under the control of abank of which the user on the first client computer 12 a is a customer.It may be possible that the second server computer 14 b is masqueradingas the first server computer 14 a in a phishing attempt, and the firstclient computer 12 a may have been misdirected to the second servercomputer 14 b. Additionally, all legitimate data transfers between thefirst client computer 12 a and the first server computer 14 a must notbe intercepted by any of the other computers, including a third clientcomputer 12 c, the second client computer 12 b, and the second servercomputer 14 b.

An aspect of the present invention relates to a method of mutuallyauthenticating the client computer 12 and the server computer 14. Withreference to the flowchart of FIG. 2 and additionally to the sequencediagram of FIG. 3, the method initiates with a step 200 of transmittinga token 26 from the client computer 12 to the server computer 14 over anunsecured data link 27. However, prior to the transmission of the token26, there may be an additional step of the client computer 12 initiatingthe unsecured connection 27 with the server computer 14. For example,the user may input the network address of the server computer 14 intothe browser application on the client computer 12, at which point arequest is made for a file or page on the server computer 14. The token26 is also referred to as a certificate request identifier, and containsa random value that identifies the particular request. As will bedescribed in further detail below, the token 26 is maintained on theserver computer 14 to ensure that only transactions referenced by thecertificate request identifier are deemed valid. It is understood thatthe random value prevents replay attacks. According to one embodiment ofthe present invention, the token 26 is accompanied by a certificateretrieval script 28, which directs the browser to begin the process ofauthenticating the client computer 12.

Thereafter, according to step 210, a secure data transfer link 30 isinitiated by the client computer 12 utilizing a full requested UniformResource Locator (URL) 32. In accordance with a preferred embodiment,the secure data transfer link 30 is a symmetric TLS link. In furtherdetail with reference to the sequence diagram of FIG. 4, the clientcomputer 12 initiates a connection to the server computer 14 bytransmitting a synchronize, or SYN packet 34. Thereafter, the servercomputer 14 transmits a synchronize and acknowledge, or SYN+ACK packet36 to the client computer 12. Upon receipt, the client computer 12re-sends an acknowledge, or ACK packet 38 to the server computer 14. Asunderstood, the foregoing transmissions relate to the TransmissionControl Protocol (TCP), a protocol layer underneath the TLS protocol.

Upon establishing a TCP connection between the client computer 12 andthe server computer 14, a CLIENT_HELLO command 40 is sent from theclient computer 12 to the server computer 14. This packet includes thehighest version of TLS supported by the client computer 12, the ciphersand data compression methods supported by the client computer 12, asession identifier, and random data. Upon receipt of the CLIENT_HELLOcommand 40, the server computer 14 transmits a SERVER_HELLO command 42.The SERVER_HELLO command 42 includes the version of TLS, cipher, anddata compression method that has been selected. Additionally, thepreviously set session identifier is included, as well as additionalrandom data. Thereafter, the server computer 14 transmits theCERTIFICATE command 44, which includes a server certificate 46, and aSERVER_DONE command 48, which indicates that the server computer 14 hascompleted this handshaking phase.

The server certificate 46 is understood to be in conformance with theX.509 standard. More particularly, with reference to FIG. 5, the datastored in the server certificate 46 includes a version number 51, aserial number 52, an issuer identifier 54, a validity identifier 55, asubject public key information 57 including a public key algorithmidentifier 57 a and a subject public key 57 b, and a certificatesignature 59. The version number 51 identifies the version of the X.509standard being used for the particular certificate, while the serialnumber 52 is a unique number assigned by a particular CA. The issueridentifier 54 includes the name of the CA that issued the certificate,and a validity identifier 55 includes a validity date range with earlierand later limits. The subject identifier 56 contains the name of aperson, group, or organization to which the certificate was issued. Thesubject public key algorithm identifier 57 a denotes the algorithm usedto generate the subject public key 57 b, and the subject public key 57 bcontains the public key associated with the certificate. The certificatesignature 59 contains a signature as generated by the CA. As furtherunderstood, the server certificate 46 includes a corresponding serverprivate key 50.

After verifying the authenticity of the sever certificate 46, the clientcomputer 12 transmits a CERTIFICATE_VERIFY command 66. Additionally, theclient computer 12 transmits a first CHANGE_CIPHER SPEC command 68,followed immediately by a first FINISHED command 70. This indicates thatthe contents of subsequent TLS record data sent by the client computer12 during the current session will be encrypted. It is understood thatthe first FINISHED command 70 includes a digest of all handshakecommands previously transmitted to ensure that no alteration occurred.Next, the server computer 14 transmits a second CHANGE_CIPHER_SPECcommand 72, followed immediately by a second FINISHED command 74. Likethe first CHANGE_CIPHER_SPEC command 68, the second CHANGE_CIPHER SPECcommand 72 indicates that subsequent TLS record data sent by the servercomputer 14 during the current session will be encrypted. The secondFINISHED command 74 includes all prior handshake commands from theserver computer 14 to the client computer 12. The client computer 12transmits a generated symmetric key that is encrypted with the subjectpublic key 57 b in the server certificate 46. The server private key 50is used to decrypt to the symmetric key upon receipt by the servercomputer 14, and subsequent transmissions to the client computer 12 willbe encrypted therewith.

As indicated above, the client computer 12 securely retrieves the servercertificate 46 in accordance with an aspect of the present invention.Specifically, according to the process of establishing the TLSconnection 30 between the client computer 12 and the server computer 14,the server certificate 46 is transmitted. In one embodiment, the clientcomputer 12 stores the server certificate 46 for use outside the contextof the TLS connection 30, as will be detailed further below.

Referring back to FIGS. 2 and 3, the method for mutually authenticatingthe client computer 12 and the server computer 14 continues with a step220 of transmitting a response packet 76 to the server computer 14. Infurther detail as shown in FIG. 6, the response packet 76 is comprisedof the full requested URL 32, the token 36, the server certificate 46,and a client certificate 78. The structure of the client certificate 78is identical to that of the server certificate 46, and as shown in FIG.5, includes the version 51, the serial number 52, the issuer 54, thevalidity identifier 55, the subject identifier 56, the subject publickey information 57 a,b, and the certificate signature 59. According toone embodiment of the present invention, the Microsoft CryptoAPIlibraries are utilized to retrieve the client certificate 78 from acertificate storage location. Like the server certificate 46, the clientcertificate 78 also has a corresponding private key, a client privatekey 80. The response packet 76 includes an additional authenticationidentifier correlated to the private client key 80. According to oneembodiment of the present invention, such authentication identifier is acryptographic hash 77 of the contents of the response packet 76. By wayof example only and not of limitation, the Message Digest Algorithm-2(MD2) hash function is used, though any other hash function such asMessage Digest Algorithm-5 (MD5), Secure Hash Algorithm (SHA) or thelike may be substituted without departing from the scope of the presentinvention. The resulting cryptographic hash 77 is signed with theprivate client key 80

According to step 230, the method further includes validating thecontents of the response packet 76. First, the authenticity of theresponse packet 76 itself is verified. As indicated above, the responsepacket 76 includes the cryptographic hash 77 that has been signed withthe private client key 80. With reference to the flowchart of FIGS. 7a-7 c, according to step 300, the client-side cryptographic hash 77 a isdecrypted using the client certificate 78. A server-side cryptographichash is computed for the response packet 76 as existing on the server14. The server-side cryptographic hash is compared against theclient-side cryptographic hash 77 accompanying the response packet 76per comparison step 312. If the values do not match, then the responsepacket 76 is deemed to have been tampered with, and any connections areterminated as in step 315. If the values match, further verification ofthe contents of the response packet 76 continues as will be describedbelow.

Such further verification includes comparing the constituent parts ofthe response packet 76 with known copies thereof. First, the signatureof the client certificate 78 is validated per step 320, where thesubject public key information 57 b is verified. Thereafter, thecertificate signature 59 and the issuer identifier 54 are examined toconfirm that a properly recognized CA has signed the client certificate78 per step 330. The subject identifier 56 is also examined to confirmthat the client certificate 78 was issued to a properly recognizedorganization according to step 340. According to one embodiment, aproperly recognized organization refers to a legitimate organizationhaving control over the server computer 14. Additionally, the clientcertificate 78 is confirmed to be valid and unexpired by comparing thevalidity identifier 55 of the client certificate 78 against the currentdate per step 350. If any of the foregoing validation step fails, theclient certificate 78 is deemed to have been tampered with, and dropsthe connection per step 315.

The remaining components in the response packet 76 is also verified,including the full requested URL 32, the token 26, and the servercertificate 46. As described above, the token 26, or the certificaterequest identifier is stored in the server computer 14. Per step 360,such stored value of the token 26 is compared against value of the token26 in the response packet 76. It is understood that matching valuesconfirms that no replay attacks are taking place. With respect to thefull requested URL 32 in step 370 the value thereof is verified againstthe actual URL of the server computer 14. This is understood to verifythat no phishing attacks are taking place that redirect the clientcomputer 12 to a malicious server. With respect to the servercertificate 46 included in the response packet 76, per step 380 it iscompared against the server certificate 46 residing on the servercomputer 14. This prevents man-in-the-middle attacks, as a differentserver certificate 46 from the one stored on the server computer 14 asopposed to the one being returned via the response packet 76. Alongthese lines, if any of the foregoing verifications fails, the connectionbetween the server computer 14 and the client computer 12 is immediatelybroken, and no further access to the server computer 14 is permitted. Ifthere are no anomalies, however, the client computer 12 is authenticatedand continues to access the server computer 14. As will be appreciated,the foregoing verifications discover one or more security breaches.

With reference to FIG. 8, according to another aspect of the presentinvention, the client computer 12 includes a client authenticationmodule 82, and the server computer 14 includes a server authenticationmodule 84. The client authentication module 82 is understood to handlethe processes on the client side as discussed above, including retrievalof the token 26, the script 28, the server certificate 46, and theclient certificate 78, as well as the transmitting of the responsepacket 76 after signing the same with the private client key 80.According to one embodiment, the client authentication module 82 is anActive-X component that is installed with a single user interaction viathe web browser on the client computer 12. However, alternativeexecutable components that may be added on to the browser are alsodeemed to be within the scope of the present invention. The serverauthentication module 84 is understood to handle the processes on theserver side as discussed above, including transmission of the token 26and the server certificate 46, as well as the validation of the receivedresponse packet 76. Thus, the client authentication module 82 and theserver authentication module 84 communicate with each other, andtogether implement an X.509 authentication scheme without the deploymentof client-side TLS.

It will be appreciated that the aforementioned method presupposes that aclient certificate 78 and a corresponding private client key 80 alreadyexist on the client computer 12. The server authentication module 84 maydetermine whether or not the client certificate 78 exists on the clientcomputer 12, and if not, the server authentication module 84 alerts acertificate server 86. Prior to issuing a client certificate and aprivate client key to the client computer 12, the user associatedtherewith is authenticated via an out-of-band modality. According to oneembodiment, the server authentication module 84 notifies a telephonyserver 88 to deliver a one-time password to a cellular phone or alandline phone under the control of the user. Alternatively, an e-mailor a Short Message Service (SMS) text message may be sent. Otherout-of-band authentication techniques are contemplated, such as voicerecognition, IP address verification, and the like. The entry of theone-time password may be handled through the server computer 14 with theserver authentication module 84. In lieu of, or in addition to theforegoing out-of-band authentication, the user may be presented with anadditional knowledge-based authentication. For example, the user may beasked about their favorite color, the high school they attended, andother similar questions.

Upon supplying the correct response, the server authentication module 84directs the certificate server 86 to generate a private client key and acorresponding client certificate, and store it on the client computer12. The additional authentication information may be stored in anenterprise database 90 for later retrieval and use by the serverauthentication module 84. It is understood that the foregoing procedure“registers” the browser on the client computer system 12 with the servercomputer 14, effectively making such browser a second authenticationfactor (“Something the user has”).

As indicated above, the issuer identifier 54 is examined to confirm thata properly recognized CA has issued and signed the client certificate78. According to the embodiment shown in FIG. 8, the certificate server86 is the CA, and is understood to be within the control of a legitimatethird party provider separate from the organization managing the servercomputer 14 and the enterprise database 90. In an alternativeconfiguration shown in FIG. 9, the certificate server 86 and thetelephony server 88 are managed and maintained by the same organizationmanaging the server computer 14. In yet another configuration shown inFIG. 10, secure access is being enabled for web services 92. Asunderstood, the term web service 92 refers to a standardized system forsupporting machine to machine interaction. In this case, the clientcomputer 12 utilizes the client authentication module 82 to authenticatewith the server computer 14. The client certificate 78 thus generated isutilized to authenticate a W3 client to authenticate with the webservice 92 via the client certificate 78.

In addition to the foregoing configurations, it is expresslycontemplated that the client authentication module 82 and the serverauthentication module 84 may be integrated into a wide variety ofapplications requiring bi-directional authentication. By way of exampleonly and not of limitation, these include .NET forms authentication in.NET applications, Microsoft Outlook Web Access, and MicrosoftSharepoint, as well as any other system with enforcement points thatrequire proper client and server authentication.

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show any more detail than is necessary for the fundamentalunderstanding of the present invention, the description taken with thedrawings making apparent to those skilled in the art how the severalforms of the present invention may be embodied in practice.

What is claimed is:
 1. A method comprising: receiving a request for aUniform Resource Locator (URL) identifier; generating a unique sessionidentifier; transmitting over a first TCP connection, a token includingthe unique session identifier, said token signed with a private keyassociated with a server certificate; receiving a first response totransmitting the token comprising a request to initiate a secure datatransfer link over a second TCP connection, the second TCP connectionbeing distinct from the first TCP connection; completing the secure datatransfer link in response to the request to initiate the secure datatransfer link, wherein completing the secure data transfer linkcomprises transmitting the server certificate and the Uniform ResourceLocator (URL) identifier over the second TCP connection; receiving asecond response including (1) the URL identifier transmitted during thecompleting of the secure data transfer link, (2) a second certificatedistinct from the server certificate, (3) the server certificate astransmitted during the completion of the secure data transfer link, (4)the token, and (5) an authenticity identifier corresponding to a secondprivate key associated with the second certificate; and validating thesecond response, said method performed by a computing system thatcomprises one or more computing devices.
 2. The method of claim 1,wherein the authenticity identifier comprises a cryptographic hash ofthe second response, the authenticity identifier being signed with thesecond private key.
 3. The method of claim 1, wherein validating thesecond response further includes validating the requested URL identifierin the second response against a URL associated with an authenticationprocess.
 4. The method of claim 1, wherein validating the secondresponse further includes validating the token in the second responseagainst a stored token.
 5. The method of claim 1, wherein validating thesecond response further includes validating a first copy of the servercertificate stored in the server against the server certificate in thesecond response.
 6. The method of claim 1, wherein validating the secondresponse further includes validating the second certificate against theauthenticity identifier comprising a signature on the second response,the signature on the second response being associated with the secondprivate key.
 7. The method of claim 1, wherein the second responsecomprises a response packet.
 8. A method for authenticating an identityto a server comprising one or more computing devices, the methodcomprising: transmitting a request for a Uniform Resource Locator (URL)identifier; receiving a token from the server over a first data link,the token including a unique session identifier generated by the server,said token signed with a private server key associated with a servercertificate; initiating a secure data transfer link to the server inresponse to receiving the token; receiving, from the server, the servercertificate and the requested Uniform Resource Locator (URL) identifieras initially transmitted during completion of the secure data transferlink; and transmitting to the server a response including (1) therequested URL identifier, (2) a second certificate, (3) the servercertificate as received from the server during completion of the securedata transfer link, (4) the token, and (5) an authenticity identifiercorresponding to a second private key, the second private key beingassociated with the second certificate.
 9. The method of claim 8,wherein the authenticity identifier comprises a cryptographic hash ofthe response, the authenticity identifier being signed with the secondprivate key.
 10. The method of claim 8, wherein: the second certificateis issued from a certificate server associated with an authorizedcertification authority; and the second certificate is linked to anorganization associated with the server.
 11. The method of claim 10,wherein prior to issuing the second certificate, the method furthercomprises validating the identity with a challenge-response sequence.12. The method of claim 11, wherein the challenge-response sequencecomprises a response that is transmitted to a predetermined telephonedevice associated with the identity.
 13. The method of claim 11, whereinthe challenge-response sequence comprises a response that is transmittedto a predetermined e-mail address associated with the identity.
 14. Asystem for authenticating an identity, the system comprising: acomputing system comprising one or more computing devices, saidcomputing system programmed via executable instruction to at least:generate a unique session identifier; transmit a token to a secondcomputer over a first data link, the token including the unique sessionidentifier, said token signed with a private server key associated witha server certificate; establish a secure data transfer link upon arequest from the second computer, wherein establishing the secure datatransfer link comprises transmitting to the second computer the servercertificate and a Uniform Resource Locator (URL) identifier as specifiedby the second computer; receive from the second computer a responseincluding (1) the URL identifier, (2) a second certificate, (3) theserver certificate as transmitted to the second computer duringestablishment of the secure data transfer link, (4) the token, and (5)an authenticity identifier corresponding to a second private key, thesecond private key being associated with the second certificate; andvalidate the response.
 15. The system of claim 14, wherein theauthenticity identifier comprises a cryptographic hash of the response,the authenticity identifier being signed with the second private key.16. The system of claim 14, wherein validating the response furtherincludes validating the URL identifier in the response against a URLassociated with the one or more computing devices.
 17. The system ofclaim 14, wherein validating the response further includes validatingthe token in the response against a token stored by the one or morecomputing devices.
 18. The system of claim 14, wherein validating theresponse further includes validating a first copy of the servercertificate stored in the one or more computing devices against a secondcopy of the server certificate in the response.
 19. The system of claim14, wherein validating the response further comprises validating thesecond certificate against the authenticity identifier comprising asignature on the response, the signature being associated with thesecond private key.
 20. Non-transitory computer storage that comprisesexecutable instructions that direct a computing system to at least:receive a request for a Uniform Resource Locator (URL) identifier at aserver; transmit over a first data link a token including a uniquesession identifier generated by a server and signed with a privateserver key associated with a server certificate; receive a firstresponse to transmitting the token comprising a request for a securedata transfer link; initiate a secure data transfer link in response tothe request for a secure data transfer link, the secure data transferlink being independent of the first data link; complete the secure datatransfer link, the server certificate and the requested Uniform ResourceLocator (URL) identifier of the server being transmitted duringcompletion of the secure data transfer link; receive a second responseincluding (1) the requested URL identifier of the server transmittedduring the completion of the secure data transfer link, (2) a secondcertificate, (3) the server certificate as received from the serverduring the completion of the secure data transfer link, (4) the token,and (5) an authenticity identifier corresponding to a second privatekey, the second private key being associated with the secondcertificate; and validate the second response.
 21. The non-transitorycomputer storage of claim 20, wherein the authenticity identifierincludes a cryptographic hash of the second response, the authenticityidentifier being signed with the second private key.
 22. Thenon-transitory computer storage of claim 20, wherein validating thesecond response further includes validating the token in the secondresponse against a token stored by the server.
 23. The non-transitorycomputer storage of claim 20, wherein validating the second responsefurther includes validating a first copy of the server certificatestored at the server against a second copy of the server certificate inthe second response.
 24. The non-transitory computer storage of claim20, wherein validating the second response further includes validatingthe second certificate against a signature on the second response, thesignature being associated with the second private key.